The present invention relates to a method of and machine for reprofiling the periphery of a railroad-car wheel. More particularly this invention concerns the turning-down of the worn periphery of such a wheel.
A railroad-car wheel is formed as a body of revolution having an outer periphery formed at an inside axial edge with a flange and having a running surface terminating at the outside axial edge of this outer periphery. After considerable use the outer periphery wears away at the running surface between the flange and the outer edge, so that the flange projects considerably radially beyond the running surface which itself has a bulge at its outside edge.
As such railroad-car wheels are made of steel and quite expensive, it is standard practice to turn down the worn wheels so as to reprofile them, giving them a new running surface. Such reprofiling slightly reduces the diameter of the wheel, but this has been found to have practically no effect on a standard railroad-car wheel which is only mounted on a bogey and which is not driven.
In a typical machining operation the wheel is mounted in a lathe-type holder which rotates this wheel about its normal rotation axis. A tool is guided by a template having the shape to be imparted to the wheel over the surface thereof in a succession of passes, with the tool being stepped radially toward the rotation axis of the wheel between each pass. Since the wheel is typically worn most deeply between its outside edge and its flange, during the first several passes material is only removed from these regions. Only when these regions have been cut down sufficiently, can the entire outer periphery be machined in a single last pass so as to impart to it the desired profile.
Thus such an operation is relatively complex. It is impossible to turn the wheel down in a single pass, as the periphery of the wheel is of hard steel and the cutting tool can only make a cut of a maximum depth which is normally only a fraction of the maximum amount that the wheel periphery must be reduced in order to reprofile the entire outer surface thereof. For this reason the machining task is a lengthy operation, as the first several passes at least of the tool only serve to remove the high spots on the wheel periphery.